Tube and bar bending machinery



Sept. 8, 1964 c. F. HAUTAU 3,147,792

TUBE AND BAR BENDING MACHINERY Filed Sept. 25. 1961 s Sheets-Sheet 1INVENTOR.

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TUBE AND BAR BENDING MACHINERY Filed Sept. 25, 1961 3 Sheets-Sheet 3INVENTOR. 094 945.: A #40780 Q44; 1km,

United States Patent 3,147,792 TUBE AND BAR BENDING MACHINERY Charles F.Hautau, 146 Hilltop Road, Oxford, ()hio Filed Sept. 25, 1961, Ser. No.140,300 8 Claims. (til. 15346) This invention relates to a machine forbending tubing and more particularly to apparatus for bending tubing bystretching it beyond the yield strength but below the ultimate strengthof the tube material.

One method of bending tubing involves forcing the tubing about a form bymeans of a wiper bar. Due to the tendency of the metal on the insideface of the bend to buckle or wrinkle and since such wrinkling dependson the ratio between pipe diameter and wall thickness, this conventionalmethod is limited as to the size and type of tubing which may besuccessfully bent. One method of preventing such wrinkling is tosimultaneously bend the metal and stretch it beyond its yield or elasticlimit but below its ultimate or breaking strength. When stretched beyondits yield strength, metal becomes plastic and is readily bent to newshapes. By stretch forming tubing, therefore, the plasticity of themetal above its yield strength is utilized to prevent wrinkling orbuckling of the tube walls. In addition, this cold working of the metalwork hardens it and results in a substantial increase in the strengthand hardness of the material.

The present invention contemplates a device for simultaneouslystretching the tubing beyond its yield strength and bending the tubingabout an annular form through a desired arc distance. In two preferredembodiments of the present invention which will subsequently be described in detail, the workpiece is placed in the machine and positionedfor bending by a series of clamps and hydraulic motors in a mannersimilar to that described in my pending application Serial No. 16,846.After the workpiece is firmly clamped in position so as to preventmovement along its axis, a bending clamp locks the tube against anannular form and both the clamp and form rotate about the axis of theform. A hydraulic cylinder resists the tendency of the form and bendingclamp to Walk back along the tube. The tubing is therefore stretched asit is bent around the form. The cylinder is set to allow such walkingonly when the force exerted on the tube is in excess of the yield limitbut less than the ultimate limit of the metal.

It is therefore an object of this invention to provide means forsimultaneously bending tubing and stretching it beyond the yieldstrength, but below the ultimate strength, of the tube material.

Another object of the present invention is to provide a machine having aseries of rotatable bending forms, an arm which clamps the workpiece tothe forms, means for clamping the tubing to prevent longitudinalmovement, means for rotating the form and the arm and means forpreventing the forms and arm from walking back along the tube until apredetermined stress is exerted on the bent portion of the tubing.

Another object of this invention is to provide means for preventing theformation of wrinkles on the inside wall of the bend during bendingoperations.

A further object of the present invention is to provide means for workhardening the tubing during the bending operation.

Further objects of the present invention Will be made apparent by thefollowing detailed description wherein are disclosed two preferredembodiments of the present invention. The description makes reference tothe accompanying drawings in which:

FIGURE 1. is a perspective view of one embodiment of the presentinvention.

FIGURE 2 is an elevational view of the bending forms shown in FIGURE 1.

FIGURE 3 is a detailed sectional view of a mandrel and support blockswhich may be employed in either of the embodiments of the presentinvention subsequently described in detail.

FIGURE 4 is a detailed sectional view of a mandrel which may be employedin either of the embodiments of the present invention.

FIGURE 5 is a detailed sectional view of the mandrel of FIGURE 4.

FIGURE 6 is a detailed sectional view of a second mandrel which may beemployed with either of the two embodiments of the present inventionwhich will subsequently be described in detail.

FIGURE 7 is a perspective view of a second embodiment of the presentinvention.

FIGURE 8 is an elevational view of the bending forms shown in FIGURE 7.

FIGURE 9 is a detailed elevational view of an alternative embodiment ofthe means for preventing the forms and bending clamp from walking backalong the tube.

With reference to the drawings, FIGURE 1 shows a preferred embodiment ofthe present invention. The machine is illustrated with the hydraulic andelectronic systems removed for simplicity. These systems may be of aclass well known to those skilled in the art and a particular variety isdescribed in greater detail in my copending application Serial No.16,846.

The machine is supported on a base 10 which may be welded plateconstruction. To the left of the machine, as shown in FIGURE 1, a pipestand 12 which is supported on two legs 14 is adapted to support thepipe 16 as it enters the machine. A mandrel snake 13 or shoe 20 isattached to the end of a flexible cable 22 which may be constructed ofsmall steel wires or of any suitable material such as will allow thecable 22 to take compressive forces over short lengths when it isstored, but will also be sufficiently flexible so as to allow the cableto easily conform to a large radius. The cable is stored in a storagetube 24 disposed parallel to the supporting structure of the machine. Apair of wheels 26, of suitable material so as to engage the cable 22, ispowered by a hydraulic motor at 28.

The cable 22 is of such length that in its retracted position, themandrel snake 18 or shoe 20 will be situated just short of the free endof the longest workpiece which the machine can accommodate. If theworkpiece is of less than this maximum length, the mandrel 18 and itsadjacent cable 22 will be required to move through some distance toreach the end of the pipe 16. To provide support for the cable 22 as itmoves through this distance, and to guide it toward the interior of thepipe 16, a series of movable blocks 30 surround the cable 22 behind themandrel 18 and move in a channel 32 disposed parallel to the extensionof the tubing 16 and slightly below it. The guide blocks 30 are fittedwith T extensions 31 of various widths which are accommodated by stops33 extending perpendicularly from the flanges of the channel 32. Whenthe cable 22 is initially energized to move the mandrel toward the freeend of the tubing 16, the guide blocks 39 are moved forward by theattraction of magnets 35 sunk in the surfaces of the blocks 30 and themandrel 18, as shown in FIGURE 4, and station themselves at regularintervals along the otherwise unsupported length of the cable 22 betweenits storage tube 24 and the tube to be bent. An alternative method ofspacing the blocks 30 consists of utilizing a series of detentattachments between the guide blocks 30 and the cable 22.

The wheels 26 and the motor 28 are arranged so as to propel the mandrel18 through the tubing to its normal station during the bending process.If a snake type manmove towards the stationary clamp 46.

33 drel 18 (FIGURE 6) is employed, the snake 18 would have to projectfrom the free end of the tube. If a shoe type mandrel 20 (FIGURE isemployed, the shoe would be disposed with its end projecting just beyondthe point at which bending begins.

A chuck 34, slidably mounted on slide rods 36, is positioned along theslide rods 36 by a hydraulic motor 38. The chuck 34 has jaws 40 whichmay be opened or closed by a hydraulic cylinder 42 or revolved by ahydraulic motor 44 by means of gears (not shown) in a manner well knownto the art. A stationary clamp 46, operated by a hydraulic cylinder 48,locks the pipe in place during the bending operation.

The bending apparatus consists of a column of annular bending forms ofvarying diameters mounted on a threaded shaft or screw 52, and an arm 54fixed so as to rotatably move about the screw 52. As shown in FIGURE 2,each of the forms 50 permits a different radius of bend. A hydraulicmotor 56 engages a gear (not shown) which is mounted on the screw 52 sothat rotation of the motor 56 revolves the screw 52 and enables thedesired bending form 50 to be moved vertically into position adjacentthe pipe 16. A bending clamp 58, operated by a hydraulic cylinder 60,locks the workpiece firmly between the clamp 58 and the form 50. Ahydraulic motor 62 rotates a pinion 64 which engages a gear 66permanently aifixed to both the forms 50 and the arm 54 in such a manneras to rotate the forms 50 and the arm 54 at the same rate. The screw 52is located in a housing 68 which is permanently aifixed to a slide block70, slidably mounted in longitudinal ways 72. The entire assembly offorms 50, arm 54, slide block 70 and longitudinal ways 72, is slidablymounted in lateral ways '74 and may be moved in the lateral ways 74 by ahydraulic motor 76. The movement of the slide block along thelongitudinal ways 72 is limited by a passive hydraulic cylinder 78 whichis preset to prevent movement of the slide block 70 until the stress inthe pipe 16 reaches a value in excess of the yield strength, but lessthan the ultimate strength, of the pipe material.

In operation, the arm 54 is swung to its open position perpendicular tothe axis of the pipe 16, with the bending clamp 58 in an open position.The bending forms 50 are raised or lowered until the form having thedesired radius of bend is at the same elevation as the pipe 16. Theentire assembly of forms 50, arm 54, slide block 70, and longitudinalways 72 is moved laterally until the bending form 50 is immediatelyadjacent to the pipe 16. The cable 22 and snake 18 or shoe 20 areretracted (to the left in FIGURE 1) and the stationary clamp 46 openedso as to allow the pipe 16 to be placed in the chuck 34. The hydrauliccylinder 42 and motors 38, 44 are activated, positioning the desiredpoint on the pipe 16 between the bending clamp 58 and the forms 50. The

stationary clamp 46 is closed and the cable 22 moved forward (to theright in FIGURE 1) until the snake 18 or shoe 20 is disposed at thepoint of bending. The bending clamp 58 is closed, locking the pipe 16between the clamp 58 and the form 50. The hydraulic motor 62 isactivated, rotating the arm 54 and forms 50, pulling the pipe 16 aroundthe form 50.

Due to the resistance in the pipe length between the stationary clamp 46and the forms 50, there is a tendency for the arm 54 and forms 50 tomove or walk towards the stationary clamp 46 as the pipe 16 is pulledaround the forms 50. The hydraulic cylinder 78 resists such movementwith the result that the pipe 16 is stretched between the bending clamp58 and the stationary clamp 46. When the stress on the pipe 16, andhence the force on the slide block 70, reaches a predetermined value inexcess of the yield stress but less than the ultimate strength of thepipe material, the resistance of the cylinder 78 is overcome and the arm54, forms 50, and slide block 70, The pipe 16 is 4 thus simultaneouslybent and stretched past its yield limit but below its ultimate limit.

In an alternative method (FIGURE 9) of providing resistance to themovement of the forms 44 towards the clamp 40, a gear 130 is fixed tothe screw 52 so that it engages a stationary rack 132. The rotation ofthe forms 44 would then walk the entire bending section toward the clampalong the rack. The ratio of the diameter of the column of forms 44 tothe diameter of the driving gear would then determine the tension thatis applied to the tubing. This ratio could be calculated to stretch thetubing with a stress above the yield stress but below the ultimate limitof the metal.

After the arm 54 and forms 50 have rotated through the desired arcdistance, the bending clamp 58 is opened and the chuck assembly 34, 40actuated to rotate the pipe 16 and move it forward (to the right inFIGURE 1) along its axis to its new desired position adjacent the forms50. The bending operation is then repeated.

FIGURE 7 illustrates a second embodiment of the present invention, inwhich a cylindrical column of bending forms 80 is utilized, each formthus permitting the same radius of bend, but suitable for bending pipeof a different diameter. A mandrel assembly is comprised of a cable 82disposed to be engaged and moved by wheels 84. The cable 82, whichterminates in a mandrel 86, is stored in a tube 83 and supported alongits length by a series of movable blocks 90. A chuck assembly indicatedgenerally at 92 positions the pipe 94 before the forms 80. A stationaryclamp 96 locks the pipe 94 in position during the bending operation.

The bending apparatus consists of the cylindrical column of annularbending forms 80 mounted on a screw 98 so as to be moved vertically asthe screw 98 is rotated by a hydraulic motor 100. A bending clamp 102,mounted on an arm 104 disposed to rotate about the axis of the forms 80,locks the pipe 94 against the forms 80. A hydraulic motor 106 rotates apinion 108 which engages a gear 110 permanently aflixed to both theforms 80 and the arm 104 in such a manner as to rotate the forms 80 andthe arm 104 at the same rate. The screw 98 is located in a housing 112which is permanently afiixed to a pressure block 114, slidably mountedon the extensions of slide rods 116.

As the arm 104 and forms 80 rotate, the resistance in the pipe 94 tendsto pull the arm 104 and forms 80 towards the stationary clamp 96. Thismovement is limited by a hydraulic cylinder 118 connected to thepressure block 114. The cylinder 118 resists movement of the pressureblock 114 until the stress in the pipe material reaches a value inexcess of the yield strength but less than the ultimate strength of thematerial.

In operation, the cable 82 is retracted and the pipe placed in themachine and positioned for bending. The desired bending form is movedvertically into position and the stationary clamp 96 closed. The mandreland cable 82 are moved forward into position, the bending clamp 102locked, and the arm 104 and form 80 rotated about the axis of the forms80. The hydraulic cylinder 118 resists the tendency of the arm 104 andforms 80 to walk back towards the stationary clamp 96. The pipe 94 isthus simultaneously bent and stretched past its yield limit but belowits ultimate limit.

If the shoe mandrel 20 (FIGURE 5) is utilized with either of the aboveembodiments of the present invention, means must be provided to retractthe mandrel 20 at the same rate that the forms 50 and the arm 54 walkback towards the stationary clamp 46. This may be accomplished byconnecting the hydraulic motor 28 which moves the cable to the fiuidrelief valve in the passive hydraulic cylinder 78 in such a manner thatthe wheels 26 will retract the cable 22 and mandrel 20 when fluid isforced out of the hydraulic cylinder 78. If the snake mandrel 18 (FIGURE6) is employed, such retracting means are not necessary since the snake18 may be bent with the pipe around the form 50.

For bends of large radii or of radii other than those on the column ofbending forms, an incremental bending technique may be utilized witheither of the above embodiments of the present invention. This techniqueconsists of forming a series of small arc bends in close proximity withone another so as to form the longer desired radius of bend.

Although the above embodiments illustrate the present inventionincorporated in an automatic stretch bending machine, the invention mayalso be successfully employed in machines of the non-automatic varietyand in machines which employ different bending techniques. The presentinvention is also adaptable to stretch bending solid rods or shafts inaddition to hollow tubes or pipes.

The mandrel equipment shown in the above embodiments is not necessaryfor the successful stretch bending of all sizes and varieties of tubing.Although the mandrel adds extra support for the metal on the inside faceof the bend during the bending operation, the necessity for such supportwould depend on the particular tubing to be bent.

This invention may be embodied in other forms or carried out in otherways without departing from the spirit or essential characteristicsthereof. The present embodiments of the invention are therefore to beconsidered as in all respects illustrative and not restrictive, thescope of the invention being indicated by the appended claims, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

Having thus described my invention, I claim:

1. A machine for bending an elongated member, comprising: a support forsaid member; a bending form having its axis extended perpendicularly tothe axis of Said elongated member, said form being rotatable about itsaxis and movable in a direction parallel to the extension of saidmember; a first clamp operative to restrain a first point on the lengthof said elongated member from movement with respect to said support; asecond clamp operative to clamp a second point on said elongated memberagainst the perimeter of said bending form, said second clamp beingrotatable about the axis of said bending form and movable in a directionparallel to the extension of said member; means for rotating saidbending form and said second clamp about the axis of said bending formso that a section of said elongated member between said first and secondpoints is pulled around said bending form thereby stressing said memberbetween said first and second points; and means for restraining motionof said bending form and said second clamp in the direction parallel tothe axis of said elongated member in such a manner that the motion ofsaid bending form and said second clamp toward said first clamp occursonly upon the imposition of a predetermined stress upon the memberbetween said first and second points.

2. A machine for bending an elongated member, comprising: a support forsaid member; a bending form having its axis extending perpendicularly tothe axis of said elongated member, said form being rotatable about itsaxis; a first clamp operative to restrain a first point on the length ofsaid elongated member from movement with respect to said support; asecond clamp operative to clamp a second point on said elongated memberagainst the perimeter of said bending form, said second clamp beingrotatable about the axis of said bending form; a platform supportingsaid second clamp and said bending form, said platform being movable ina direction parallel to the axis of said elongated member; means forrotating said bending form and said second clamp With respect to saidplatform and about the axis of said bending form so that a section ofsaid elongated member between said first and second points is pulledaround said bending forms, thereby stressing said member between saidfirst a 6 and second points; and means for restraining motion of saidplatform in the direction parallel to the axis of said elongated memberin such a manner that the motion of said platform toward said firstclamping means occurs only upon the imposition of a predetermined stressupon the member between said first and second points.

3. The structure defined in claim 1, wherein said means for restrainingmotion of said bending form and said second clamp in the directionparallel to the axis of said elongated member comprises: a hydrauliccylinder and piston having one end connected with respect to saidsupport and one end connected with respect to said bending form so as tocause said piston to move within said cylinder as said bending form andsaid second clamp move with respect to said support; and means forallowing motion of said piston within said cylinder only after theexercise of a predetermined force between said piston and said cylinder.

4. The structure defined in claim 1, wherein said means for restrainingmotion of said bending form and said second clamp in the directionparallel to the axis of said elongated member comprises: a gear fixedabout the axis of said bending form; means for engaging said gear insuch a manner that rotation of said bending form translates said gearand said bending form in a direction parallel to the axis of saidelongated member, said engaging means translating said gear and saidbending form through such a distance for a given rotation of the formthat a predetermined stress is exerted on said elongated member betweensaid first and second clamps.

5. The structure defined in claim 1, wherein said means for restrainingmotion of said bending form and said sec ond clamp in the directionparallel to the axis of said elongated member comprises: a gear fixedabout the axis of said bending form; a rack fixed to said support anddisposed adjacent said gear so that said gear engages and walks alongsaid rack as said bending form moves toward said first clamp, the ratioof the diameter of said bending form to the diameter of said gear beingsuch that a predetermined stress is exerted on said elongated memberbetween said first and second clamps.

6. A machine for bending an elongated member, comprising: a support forsaid member; a shaft having its axis extending perpendicularly to theaxis of said elongated member, said shaft being rotatable about its axisand movable in a direction parallel to the extension of said member; aseries of annular bending forms fixed about said shaft; means forvertically moving said shaft with respect to said support so as to bringthe desired bending form into position opposite said second clamp; afirst clamp operative to restrain a first point on the length of saidelongated member from movement with respect to said support; a secondclamp operative to clamp a second point on said elongated member againstthe perimeter of one of said bending forms, said second clamp beingrotatable about the axis of said shaft and movable in a directionparallel to the extension of said member; means for rotating said shaftand said second clamp about the axis of said shaft so that a section ofsaid elongated member between said first and second points is pulledaround one of said bending forms thereby stressing said member betweensaid first and second points; and means for restraining motion of saidshaft and said second clamp in the direction parallel to the axis ofsaid elongated member in such a manner that the motion of said shaft andsaid second clamp toward said first clamping means occurs only upon theimposition of a predetermined st-ress upon the member between said firstand second points.

7. A machine for bending an elongated member, comprising: a support forsaid member; a shaft having its axis extending perpendicularly to theaxis of said elongated member, said shaft being rotatable about its axisand movable both in a direction parallel to the extension of said memberand in a direction perpendicular to the axis of said elongated memberand perpendicular to the axis of said shaft; a series of annular bendingforms of varying diameter fixed about said shaft; means for moving saidshaft vertically with. respect to said support and in a directionperpendicular to the axis of said elongated member and perpendicular tothe axis of said shaft, so as to bring the desired bending form intooperative position; a first clamp operative to restrain a first point onthe length of said elongated member from movement with respect to saidsupport; a second clamp operative to clamp a second point on saidelongated member against the perimeter of one of said bending forms,said second clamp being rotatable about the axis of said shaft andmovable in a direction parallel to the extension of said member; meansfor rotating said shaft and said second clamp about the axis of saidshaft so that a section of said elongated member between said first andsecond points is pulled around one of said bending forms therebystressing said member between said first and second points; and meansfor restraining motion of said shaft and said second clamp in thedirection parallel to the axis of said elongated member in such a mannerthat the motion of said shaft and said second clamp toward said firstclamping means occurs only upon the imposition of a predetermined stressupon the member between said first and second points.

8. A machine for bending tubing, comprising: a support for said tubing;a bending form having its axis extending perpendicularly to the axis ofsaid tubing, said form being rotatable about its axis and movable in adirection parallel to the extension of said tubing; a first clampoperative to restrain a first point on the length of said tubing frommovement with respect to said support; a second clamp operative to clampa second point on said tubing against the perimeter of said bendingform, said second clamp being rotatable about the axis of said bendingform and movable in a direction parallel to the extension of saidtubing; means for rotating said bending form and said second clamp aboutthe axis of said bending form so that a section of said tubing betweensaid first and second points is pulled around said bending form therebystressing said tubing between said first and second points; means forrestraining motion of said bending form and said second clamp in thedirection parallel to the axis of said tubing in such a manner that themotion of said bending form and said second clamp toward said firstclamp occurs only upon the imposition of a predetermined stress upon thetubing between said first and second points; a mandrel movable along theaxis of said tubing; a stationary support for said mandrel; means formoving said mandrel with respect to said support forward into theinterior of said tubing until said mandrel is situated adjacent theinterior wall of said tubing at said second point on said tubing; andmeans for retracting said mandrel at the same rate that said bendingform and said second clamp move towards said first clamp.

References Cited in the file of this patent UNITED STATES PATENTS 81,902Heckart Sept. 8, 1868 828,338 Reynolds Aug. 14, 1906 2,306,224 ParkerDec. 22, 1942 2,382,745 Powers Aug. 14, 1945

1. A MACHINE FOR BENDING AN ELONGATED MEMBER, COMPRISING: A SUPPORT FORSAID MEMBER; A BENDING FORM HAVING ITS AXIS EXTENDED PERPENDICULARLY TOTHE AXIS OF SAID ELONGATED MEMBER, SAID FORM BEING ROTATABLE ABOUT ITSAXIS AND MOVABLE IN A DIRECTION PARALLEL TO THE EXTENSION OF SAIDMEMBER; A FIRST CLAMP OPERATIVE TO RESTRAIN A FIRST POINT ON THE LENGTHOF SAID ELONGATED MEMBER FROM MOVEMENT WITH RESPECT TO SAID SUPPORT; ASECOND CLAMP OPERATIVE TO CLAMP A SECOND POINT ON SAID ELONGATED MEMBERAGAINST THE PERIMETER OF SAID BENDING FORM, SAID SECOND CLAMP BEINGROTATABLE ABOUT THE AXIS OF SAID BENDING FORM AND MOVABLE IN A DIRECTIONPARALLEL TO THE EXTENSION OF SAID MEMBER; MEANS FOR ROTATING SAIDBENDING FORM AND SAID SECOND CLAMP ABOUT THE AXIS OF SAID BENDING FORMSO THAT A SECTION OF SAID ELONGATED MEMBER BETWEEN SAID FIRST AND SECONDPOINTS IS PULLED AROUND SAID BENDING FORM THEREBY STRESSING SAID MEMBERBETWEEN SAID FIRST AND SECOND POINTS; AND MEANS FOR RESTRAINING MOTIONOF SAID BENDING FORM AND SAID SECOND CLAMP IN THE DIRECTION PARALLEL TOTHE AXIS OF SAID ELONGATED MEMBER IN SUCH A MANNER THAT THE MOTION OFSAID BENDING FORM AND SAID SECOND CLAMP TOWARD SAID FIRST CLAMP OCCURSONLY UPON THE IMPOSITION OF A PREDETERMINED STRESS UPON THE MEMBERBETWEEN SAID FIRST AND SECOND POINTS.